There are many piping networks wherein it is necessary to determine if the valves in the network are leaking. For example, pipes in ships and nuclear power plants have safety valves in them which are also used in cases of emergencies to stop all flow through the pipes. Naturally, these safety valves must not leak when they are closed. Since these valves are usually not used except in emergencies, they sometimes deteriorate due to lack of use. Therefore, it is standard practice to leak test these valves at periodic intervals.
The usual way to leak check a valve requires that the valve be closed and the pipe downstream of the valve be drained and connected to a leakage measuring device to determine the amount of leakage past the valve. This means that flow through the pipe is stopped, which means that the system incorporating that pipe is shut down. Many other pipes are usually also connected to this pipe downstream of the valve, which must also be shut off. However, their shut-off valves might also leak, and contribute to the flow past the leakage measuring device. Therefore, two valves in series in each of these connected pipes must be closed in order to completely prevent flow through these pipes. Numerous valves in interfacing systems thus have to be shut down, especially when cooling systems are involved. The ship must therefore be alongside a tender, in drydock, or in a shipyard when valves are leak checked by this method. The present invention allows these valves to be leak checked while the pipeline is in use, thereby preventing the need for shutting down the whole system when the valves are checked.